Report on Ijen (Indonesia) — 14 December-20 December 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
14 December-20 December 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Ijen (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 December-20 December 2011. Smithsonian Institution and US Geological Survey.
8.058°S, 114.242°E; summit elev. 2769 m
All times are local (unless otherwise noted)
CVGHM reported that during 1 October-30 November white plumes from Ijen rose 50-150 m above the crater and lake water temperatures ranged from 26 to 31.6 degrees Celsius. During 1-14 December brownish-white plumes rose 50-200 m above the crater. The lake water temperature was 26.8 and 34.2 degrees Celsius on 8 and 14 December, respectively. Based on increased seismicity, visual observations, and lake water temperature increases, CVGHM raised the Alert Level from 1 to 2 (on a scale of 1-4). During 15-17 December seismicity significantly increased and sulfur dioxide gas emissions around the lake also increased. On 17 December the color of the lake water changed from light green to white. The Alert Level was raised to 3 the next day.
Geological Summary. The Ijen volcano complex at the eastern end of Java consists of a group of small stratovolcanoes constructed within the large 20-km-wide Ijen (Kendeng) caldera. The north caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi, which forms the high point of the complex. Immediately west of the Gunung Merapi stratovolcano is the historically active Kawah Ijen crater, which contains a nearly 1-km-wide, turquoise-colored, acid lake. Picturesque Kawah Ijen is the world's largest highly acidic lake and is the site of a labor-intensive sulfur mining operation in which sulfur-laden baskets are hand-carried from the crater floor. Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of cones forms an E-W zone across the southern side of the caldera. Coffee plantations cover much of the caldera floor, and tourists are drawn to its waterfalls, hot springs, and volcanic scenery.